What gave you that impression? I'd say approximately 0 people from the Go community and at most 2 people from Rust expected that.
Quite literally that's what Rob Pike (golang co-creator) thought was going to happen
https://commandcenter.blogspot.com/2012/06/less-is-exponenti...
I was asked a few weeks ago, "What was the biggest surprise you encountered rolling out Go?" I knew the answer instantly: Although we expected C++ programmers to see Go as an alternative, instead most Go programmers come from languages like Python and Ruby. Very few come from C++.
That's not even close to what Rob Pike wrote on his blog.
What part of "Although we expected C++ programmers to see Go as an alternative" isn't clear enough?
> I feel like languages like Go and Rust didn’t become C++ killers because they expected everyone to jump on the bandwagon and abandon all their legacy code
Abandon is not a synonymous with rewrite, last time I checked a dictionary.
Rob probably assumed Go could displace this. And it's not unreasonable to assume so, although it's closer to a better Java, than a better C++ for this.
Instead it displaced Python for this (not for research/NumPy/Colab stuff), maybe some Java (where it's easier to containerize).
And if it did displace C++, it was in greenfield projects, with non-C++ developers. So it didn't necessarily convert any C++ developers at all.
I could easily imagine him thinking Go could make inroads there. But then it took a very long time to get a flume port, and even then it didn't have half of the nice affordances that the C++ version did.
People say they need the efficiencies of C++, but IMHO they really don't when so much of the actual code time is spent slurping data from one sstable and writing it to the next sstable.